Flow-through stripping chronopotentiometry for the monitoring of mercury in waste waters

A simple method for the determination of total mercury in waste waters is described. It makes use of a flow system incorporating a wall-jet cell equipped with a gold working electrode. The untreated sample is mixed on-line with the acidic carrier electrolyte which contains potassium permanganate and transforms the various species of mercury, especially elementary Hg, to Hg(II). The pre-treated solution enters the cell where mercury is deposited on the gold electrode. In the next step the deposit is stripped at constant current and the time corresponding to the dissolution of the deposit is obtained from the chronopotentiometric signal. The method enables it to determine and monitor Hg in the concentration range of 1 to 1000 μg/L in 5 min intervals.